1. Field of Invention
The present invention relates to improvements in the manufacture of substantially tamper-proof personal identification documents, and more particularly to improved methods and apparatus for electrophotographically personalizing identification documents.
2. Description of Prior Art
There has long existed a need for documents which authenticate that a particular person is authorized for certain privileges, financial credits, passes, etc. To effect the desired purpose, that is assuring that only the authorized person engages in the document-authorized activities, the document should accomplish at least two things. First, it should be substantially non-counterfeitable. Second, it should be readily identifiable by a monitoring agency as connected uniquely with the authorized document holder, and substantially tamper-proof with respect to alteration of this unique connective feature. In most instances it is desirable that the document be of high quality, e.g., attractive, yet producible at a reasonable cost.
There have been many approaches for achieving these objectives, increasing in complexity as new technologies evolved. One more recent approach which shows particular promise is to embed within the document detectable materials (e.g., a magnetic material) forming a code pattern which is extremely difficult to duplicate. This approach and others can accomplish the objective of substantial non-counterfeitability with respect to a number of similar documents. That is, they can be mass-produced in a central location, thus making per document costs feasible. There remains the need to "tailor" each such document to the specific person that is authorized to use it in a manner which is economical but achieves the high quality and tamper-proof aspects mentioned above.
Photographs and signatures of the authorized individual, affixed to the document have heretofore been the most common means for accomplishing this purpose. However, signatures are fairly easily forged, and most prior art techniques for affixing photographs to the non-counterfeitable core portion of documents have not satisfactorily deterred the substitution of another individual's photograph.
It has been contemplated that electrophotography may be useful as a technique for personalization of identification documents. For example British Pat. No. 1,413,832 discloses a procedure wherein an electrostatic image of a personal feature is formed on a photoconductor, transferred to the identification document and developed on that document. This technique requires image development on the identification document itself which is difficult to accomplish with good quality because of the relatively high thickness and/or internal non-uniformities of core substrates. U.S. Pat. No. 4,006,050 discloses an alternative electrophotographic technique in which an electrostatic image of the personal feature is formed on the photoconductor and developed with toner in a conventional manner, the toner image then being electrostatically transferred to a special heat sensitive release layer of an intermediate sheet and finally heat transferred onto the identification card substrate. This technique avoids the difficulties involved with developing an electrostatic image on the identification document but requires transfer of that image onto a special intermediate sheet.